Development of an ontology for laparoscopic transabdominal adrenalectomy via a comprehensive modified Delphi survey and its validation on a multicentric pilot data set for surgical training and future video analysis with machine learning algorithms


 Surgical technique is essential to ensure safe minimally invasive adrenalectomy. Due to the relative rarity of adrenal surgery, it is challenging to ensure adequate exposure in surgical training. Surgical video analysis supports auto-evaluation, expert assessment and could be a target for automatization. The developed ontology was validated by a European expert consensus and is applicable across the surgical techniques encountered in all participating centres, with an exemplary demonstration in bi-centric recordings. Standardization of adrenalectomy video analysis may foster surgical training and enable machine learning training for automated safety alerts.


decomposition into different levels of granularity with a standardized vocabulary, is therefore required to provide a machine-readable process model as a prerequisite for AI analysis of the surgical workflow 5 .To address this, we developed an ontology for multicentre use and validated its application for standardized RTLA/LTLA video analysis in a clinical pilot.
An ontology was developed by a steering committee (BS/ SDL/MR), hierarchically structuring RTLA/LTLA into five discrete phases-Preparation, Exposure, Dissection of the main adrenal vein, Dissection of the adrenal gland, Extraction and disassembling-with 27 RTLA and 25 LTLA steps (Figs S1 and S2).
For both RTLA and LTLA, a sixth phase named other intervention was added for cases of simultaneous procedures.
Senior academics (n = 17) from across Europe with >10 years of experience in adrenal surgery were invited to take part in a modified Delphi process across two rounds (Fig. S3).Panellist response rate was 88% in the first round (15/17) and 100% (15/15) in the second round.Consensus, defined as ≥80% agreement for each statement, was reached for LTLA in all 38 statements and for RTLA in 39/40 statements (97.5%;Tables S1  and S2).The content analysis of the panellists' comments identified the recurring theme of the identification of the right renal vein during RTLA as a facultative step rather than a mandatory one, depending on tumour and anatomical factors.
Two surgeons then applied the defined ontology to annotate each phase and step in 4 RTLA and 4 LTLA videos from two centres in a machine-readable format.Near-complete agreement between both surgeons was observed for the phase and step durations (Fig. 1).Video annotations revealed that completion of mandatory steps is required to proceed to the next phase, although the sequence of steps may be adapted to the individual anatomy.Procedure progression is not necessarily linear, as dissection may require interruption of a phase/step, and progress one step forward with completion of the previous step later.The supplementary material to this letter describes the key phases and steps illustrated in Video S1 (RTLA) and Video S2 (LTLA) as they would appear in a dedicated video annotation software.
In this study, we have defined a novel consensus-derived ontology for RTLA and LTLA.The ontology is suitable for standardized and multicentric video assessments as a baseline for stepwise understanding, surgical training and video analysis.The ontology will aid machine learning algorithms for future AI applications such as automated phase and step recognition, surgical skill assessment, procedural training, and ultimately 'real-time' intraoperative guidance.

Fig. 1
Fig. 1 Duration of the phases and steps in relation to the total duration of the video recordings of 4 LTLA and 4 RTLA from Strasbourg and Rome Mandatory steps are coloured, facultative steps are grey.In case of P6 (Phase 6-Other intervention), no adrenalectomy steps are present.Each video was annotated by two surgeons.The inter-annotator agreement is illustrated by an almost complete match of phase and step durations for each video.